The process of synchronizing a sampler with a received analog signal is known as timing recovery. It is a crucial component in a recording system channel detector, such as magnetic recording channel detectors. The quality of synchronization has a tremendous impact on the overall performance of the channel detector. At current areal recording densities, existing timing recovery architectures perform well. However, at the higher areal densities which will be used in the future, signal energy will be lower and noise in the system will increase. Thus, the signal-to-noise ratio (SNR) will decrease.
The advent of iterative error-correction codes allows the system to operate at low SNRs with acceptable performance due to their large coding gains. This means that timing recovery must also function at low SNRs. A conventional receiver performs timing recovery and error-correction decoding separately. Specifically, conventional timing recovery ignores the presence of error-correction codes; therefore, it fails to function properly at low SNRs, and timing errors increase.
Theoretically, joint maximum-likelihood (ML) estimation of timing offsets and message bits, which will jointly perform timing recovery, equalization and decoding, is a preferred method of synchronization; however, its complexity is gigantic. Fortunately, the solution to this problem with complexity comparable to a conventional receiver has been proposed, which is realized by embedding the timing recovery step inside the turbo equalizer so as to perform their tasks jointly. From this point on, that iterative timing recovery (ITR) scheme is denoted as “NonPSP-ITR”, where “PSP” stands for per survivor processing. However, NonPSP-ITR requires a large number of turbo iterations to provide an acceptable performance when the channel experiences severe timing jitter noise.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.